I am having the same problem, and I came to the conclusion I am actually scared of death. I don't know if it's because of my SI or something deeper within me. Whatever it is, I just hope some day I will get the courage to do it, because I know I can't keep going like this, yet I deliberately choose to delay my death, because "one more day" does inherently open possibilities of more things holding me back from CTB. And maybe I am subconsciously hoping I won't have to die, that things will be okay, that I'll wake up some day mental illness and addiction free. I know rationally that makes no sense though, yet it is what I wish for inside. Because the last thing I want is to die, I wish I could live actually, just not being me, just not being disabled. Maybe you are experiencing the same problem.
I like to think the "five stages of grief" apply to a suicidal person too, grieving their own death when they know it's going to happen. When you get past the acceptance, there's only the waiting. If you want to CTB, if you have accepted you do, eventually it's going to happen. Or at least, I hope so (for myself).
